The present invention relates to apparatus and methods for transferring powdered ore from a storage tank to a bin associated with an electrolytic cell. More specifically, the invention pertains to a method for efficient transfer of powdered ore from a storage tank to a bin associated with an electrolytic cell without excessive spillage of ore into the cell and without excessive losses to the environment.
Fluidizing conveyor systems for transferring powdered ore from storage tanks to bins associated with electrolytic cells are known in the prior art. However, each of these prior art conveying systems suffers from one or more serious disadvantages making it less than completely suitable for its intended purpose.
Two representative prior art patents relating to the conveying of powdered ore to a bin associated with an electrolytic cell are U.S. Pat. No. 3,870,374 and U.S. Pat. No. 4,016,053. In both of these patents the powdered ore is carried in an upper portion of an elongated conduit having a porous, generally horizontal partition. Pressurized air carried by a lower portion of the conduit beneath the partition passes through the partition and maintains the powdered ore in the upper portion in a fluidized state. In U.S. Pat. No. 3,870,374, the fluidizing air is vented from the upper portion of the conduit through a plurality of ceiling vents. In U.S. Pat. No. 4,016,053, a fluidizing conveyor brings powdered ore to one of several feed hoppers located above a group of electrolytic cells. The feed hoppers are provided with upwardly opening vents for directing gas and entrained dust to a suitable dust-collecting facility.
The venting systems in the above-mentioned patents have been found to operate adequately when the powdered ore contains a low proportion of particulates passing through a -325 mesh sieve. However, when used in connection with ore containing a high proportion of fines (-325 mesh material), an undue burden is placed upon the venting systems. Such burden becomes especially severe when the volume of ore transported through the fluidizing conveyor per unit time is increased.
Also known in the prior art is a venting system for fluidizing conveyors associated with electrolytic cells wherein excess fluidizing air is transmitted from the ore transport conduit through a vent into the chamber of the cell. While such venting system places smaller burdens upon a dust-collecting facility associated with the cell than the systems shown in the two above-mentioned patents, it has frequently been found that an excessive volume of ore is deposited through the vent into the cell chamber. These excessive deposits have been found to result in a reduction in operating efficiency of the electrolytic cell.
It is a principal object of the present invention to provide an apparatus for efficient transfer of powdered ore from a storage tank to a bin associated with an electrolytic cell wherein the ore is conveyed through a fluidizing conveyor, and excess fluid pressure developed in the conveyor is not released directly into the cell chamber or to a dust-collecting facility associated with the cell.
It is a related object of the invention to provide a venting system for a fluidizing conveyor associated with an electrolytic cell including a first vent interconnecting the conveyor and the bin and a second vent interconnecting the bin and the cell chamber.
A further object of the invention is to provide a pressure switch associated with the fluidizing conveyor for sensing increased fluid pressure developed in the conveyor upon filling of a bin supplied by the conveyor. In response to increased fluid pressure in the conveyor, the pressure switch shuts off a source of pressurized gas supplying the conveyor.
Another object of the invention is to provide a fluidizing pad in a conduit supplying the fluidizing conveyor, thereby allowing for high speed transfer of powdered ore to the fluidizing conveyor.
Additional objects and advantages of the present invention will become apparent to persons skilled in the art from the following specification, considered in connection with the drawings.